Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$216.64	11.868%	$242.3508	$242.35	$242.35	$242.40
Purchase #2	$75.82	5.820%	$80.2327	$80.23	$80.25	$80.20
Purchase #3	$52.83	11.675%	$58.9979	$59.00	$59.00	$59.00
Purchase #4	$116.56	5.729%	$123.2377	$123.24	$123.25	$123.20
Purchase #5	$132.69	11.611%	$148.0966	$148.10	$148.10	$148.10
Purchase #6	$30.62	10.235%	$33.754	$33.75	$33.75	$33.80
Purchase #7	$35.83	7.135%	$38.3865	$38.39	$38.40	$38.40
7 purchase totals =	$660.99		$725.0562	$725.06	$725.10	$725.10